Turbine propeller control



March 17, 1953 R. KOCHENBURGER ET L 2,631,677

TURBINE PROPELLER CONTROL 8 Sheets-Sheet l Filed Aug. 5l,

.SEIS S HSK Nh.

Q .MES

R KOCHENBURGYER ET AL 2,631,677

March 17, 1953 TURBINE PROPELLER CONTROL Filed Aug. 31, 1946 8 Sheecs-Sheerl 2 R. KOCHENBURGR ET Al. .2,631,677

March 17, 1953 TURBINE PROPELLER CONTROL Filed Aug. 3l, 1946 8 Sheets-Sheet 3 www.

um. l %\N .ENQ .Qu QNN March 17, 1953 R. KocHl-:NBURGER ET Al.

l TURBINE PROPELLER CONTROL March A17, 1953 R. KocHENBUGER ET AL 2,631,677

TURBINE PROPELLER CONTROL 8 SheetsSheet 5 Filed Aug. 5l, 1946 Nub lTylvl dbh .MISS

A NS Alllmbl MES '1l-II SQ www 8 Sheets-Sheet 6 R. 'KOCHENBURGER ET AL TURBINE PROPELLER CONTROL March 17, 1953 Filed Aug. 31, 194e QSE Bywntors l 12. lll' el' March-17, 1953 R. KOCHENBURGER ET A1. 2,631,677

TURBINE PROPELLER CONTROL Filed Aug. 31, i946 8 sheets-sheet 7 /ZZ INCR. FUWEE "0 2 R. KOCHENBURGER ET Al.

March 17, 1953 TURBINE PROPELLER CONTROL vs sheets-sheet 8 Filed Aug. 3l, 1946 Patented Mar. 17, 1953 UNITED STATES PATENT OFFICE TURBINE PROPELLER CONTROL Application August 31, 1946, Serial No. 694,398

Claims.

and coordinated control of more variables than it is necessary to control in stationary turbine installations, or with conventional aircraft reciprocating engine-propeller units, or with other 'power plants, if the combination is to yield optimum performance. Also, protection is needed against exceeding certain limits of operation if safe use of the combination is to be attained. A primary object of the invention is to provide a proper type of control system for turbo-props, while further objects include'the provision of specic mechanisms and devices which will accomplish the desired control functions when embodied in the system. Other objects will appear as the description proceeds.

The gas turbine either as a unit `assembly orA as an aggregation of components consists of a compressor which receives ambient air, pressureboosted due to ram under conditions of flight,

' and raises its pressure to several atmospheres.

Only part of the compressed air is used in the combustion chambers to combine with fuel, and the fuel-air mixture is ignited. The products of combustion mix with and raise the temperature of the balance of the air provided by the compressor, and conversely, the excess air provided by the compressor cools the combustion gases to a considerable extent. The mixed air and combustion gases are directed through a nozzle system against the blades of one or more stages of turbine wheels, which absorb a part of the energy in the hot gases, the turbine wheel temperature being controlled directly by the temperature of the mixed air and gases. The hot gases are then exhausted to the atmosphere through a jet nozzle or are otherwise disposed of. Part of the energy absorbed by the turbine may drive the compressorv and the remaining energy from the turbine drives the aircraft propeller, usually through a system of reduction gearing.

In a basic gas turbine-propeller combination the fuel flow to the combustion chambers. There are two basic measurements of operating status and power which can bemade on the turbo-prop.

(Cl. ri-135.72)

These are, R. P. M. of the turbine-compressor assembly or of the propeller, and some manifestation of turbine temperature produced. The manifestations of temperature may be measured by various means and all have a certain equivalency in indicating relative engine power in conjunction with the R. P. M. factor. The useable and measurable temperature and hence torque or power manifestations include alternatively and in part, the fuel ow, the fuel-air ratio involving mass air measurement, the temperature of the turbine wheel or other temperature indicative of turbine wheel temperature, torque or thrust delivered to or by the propeller, and propeller blade angle beta. Secondary measurements, i. e., derivative quantities or equivalent may be used for stabilizing effects, such measurements including in part turbine acceleration, rate of temperature (power) change, rate of torque change, rate of change of compressor discharge pressure and/or rate of change of fuel-air ratio.

In general, most efiicient operation of the gas turbine along with greatest power output may occur at maximum R. P. M. and at maximum allowable fuel flow as limited by maximum turbine temperatures. Structural and metallurgical limitations establish the maximum R.. P. M. and turbine temperature and the structural and metallurgical limitations therefore dei-lne the' maximum power available. Under most conditions of operation, it is to be expected that R. P. M. will be held at or near the upper limit 'to secure best operating efficiency. Throttling of the engine to partial ratings of power will ordinarily be accomplished by regulating fuel iiow to something less than the maximum allowable while maintaining preset R. P. M. which will have the eiiect of reducing torque and turbine temperatures below the maximum allowable. In the regulated operation of the turbo-prop in flight, changing conditions of air speed, air temperature and'air density will cause substantial deviations in actual turbine power if turbine temperature remains the same. This point will be explained more fully.

Objectives in evolving an adequate control system for the turbo-prop are: (1) 'I'o provide a stable and fast responding R. P. M. control with an R. P. M. selector operable by the pilot, so organized that R. P. M. errors from any selected operating R. P. M. from idle to maximum will be corrected quickly without excessive speed transients beyond the desired value. (2) To provide a manually adjustable power control, possibly graduated in percentage of permissible power from zero to the maximum available or allowable under any operating condition; with automatic regulation, so that if the power control is set at, say, 60%, substantially 60% of the then permissible maximum power will automatically be delivered at the preset R. P. lvl; At a zero power setting, a iinite turbine absolute temperature exists which varies with ambient conditions; however, it is well below maximum allowable temperature. 1 correction of errors between actual power and preset power with quickness and stability, to minimize possibilities of exceeding the turbine temperature limit or other limit. (3)A Toprovide means possibly inherent in thesystem to assure joint stability in the action of the speed and power controls.

If this sort of system is obtained, `a pilot is always able to call for more power to the maximum allowable, -with the assurance that he will get it. Without this sort or power control, the turbine might be operating at maximum temperature at a reduced power setting, and a call for more power would yield no more.

It should be realized that maximum power available from the turbine vwill vary for diiieren't combinations ci R. P. lvl., air speed, air temperature and air density although the turbine ternperature and other limits may be constant. Maximum .power regardless of its quantitative value will be that power, at any operating condition, where a maximum limit is encountered, such limits including R. P. M. turbine temperature, stress in the structure or other limiting factor. There are two predominant absolute limitsmaximum R. P. M. and maximum turbine temperature with which this invention is primarily concerned.

Where the propeller is capable of being operated to produce reverse thrust, limits of ture bine operation for very low and reverse pitch may change in character due to other limitations, although turbine temperature remains as a basic limit. Also, other parts of the turbine may impose power limitations in forward thrust operation, otherthan those imposed by turbine temperature and rotational speed.

In the correct control and regulation of the turboe'prop under the various conditions encountered in operation, any purposeful or exy ternally produced change in either R. P. M. or power (including turbine temperature) will require a coincidental change in beta and also in fuel now to prevent the introduction of permanent or transient changes in the other quantity (power or R. P. MJ. Any decrease in the mass flow of air through the turbine with respect to the fuel Iiow (except for air temperature changes that is, an increase in the fuel/air ratio, will result in turbine wheel temperature rise. Such airiiow decrease or fuel/air ratio increase may result from one or more of the iollowing changes:

a. Beta increase with consequent R. P. M. decrease.

b. Fuel flow increase.

c. Air speed decrease resulting in less ram pressure on the compressor.

An ambient air temperature increase will result in temperature increase due to lower air density and heating effect of the warmer air.

Changes above noted in the opposite sense produce the opposite effect of reducing turbine wheel The controls must also provide for To secure complete and adequate control of the power plant, automatic beta adjustment and automatic fuel iiow control are mandatory and must be interconnected with the R. P. M. and power controls operated by the pilot in such fashion as to secure properlyproportioned interaction, ywhen changes are 'made purposefully in the R. P. M. or power control, or when externally caused changes occur. They must be so interrelated vthat the sensitivities and stabilities of them will be compatible, and will not produce overall instabilityin the system, or overshoots of speed or temperature that might be harmful. in this connection, a basically stable governor when combined with a basically stable power regulator may not necessarily produce a stable systemes-they may, by their interaction, produce an unstable system or one whose response is excessively slow or oscillatory.

Referring to the simple diagram below, the two boxes on the left side represent the R. P. M. controlope'rable bythe pilot and the proportional power control operable by the pilot. The boxes on the right represent the mechanisms ioreiecting blade angle changes in the propeller, and fo'r eiecting changes in fuel flow to the turbine to be actuated by the R. P. Mfahd torque control. There inust be at least two interconnections be'- tween the boxes on the left 'and those on the right to secure complete control, either within the control system itself, or indirectly through the inuence of the system on the turbine.

Blade R. P. M. A

control angle (beta) and error sensing 2j changer Y Bl Power \\\J Fuel control f 1 flow and error sensing 'changer Whether or not a certain :pattern of linkages will comprise an adequate 'control depends on analysis of each cornbinat'icnv to determine its response characteristics; thereareseven possible basic combinations as noted below. The governving and regulating devices are automatic in character, and each one considered is assumed to lhave substantially optimum practicable ycharacteristics by itself. Even so, tendencies toward instability may result from 'a contrcl'cornbination unless compensations in the form of acceleration responses (as chosen for illustration) or other forms of derivative controls and other modifications are incorporated in the system. For convenience the symbols A, B, l and 2 are donned below and are used to indicate the functional linkages between the boxes.

mansions 1Error-"-flhediierence.between ythevnagn-itucle of the quantity called for and the magnitude existing.

, fuel flow (type Bd).

mthe control 'i3d-Fuel feed governor responsive to R. P. M.

error, having droop characteristics wherein the governor is biased to a modified setting when changes occur.

lq-Fuel regulator responsive to actual torque error.

2q-Beta regulator responsive to actual torque error.

Satisfactory and operable combinations of these control elements and linkages are:

A1 ABl B2 ABZ A12 AB12 B12 By incorporating derivative controls such as acceleration response in some of these combinations, improved performance may be secured;

-other compensations also may be included in temperature manifestation. In the case of the governor, R. P. M. deviations may cause corrections in the rate of beta change (type Al or rate of fuel flow change (type B), determined by the R. P. M. error, or by the R. P. M. error as modified by suitable acceleration indications or the equivalent.

Droop type governors may be used in which lR. P. M. deviations cause corrections in the amount of beta (type Ad) or in the amount of Auxiliary means would be included to correct the effect that a change in power requirement will change the equilibrium R. P. M. set by the governor.

In the case where a type 2q torque regulator effecting rates of change in blade-angle in response to torque deviations is combined with a type Bd droop type governor eifecting changes in fuel iiow, this combination, symbolized as Br-2q, is capable of rapid and stable response to external or purposeful disturbances, no acceleration stabilization being required. It possesses the correctible limitation for combination B-2, in that sudden changes in the setting of the R. P. M. governor can cause over-temperature conditions of short duration unless prevented by special auxiliary equipment, possibly in the form of fuel cutoff devices responsive to indications or anticipations of over-temperatures.

For a more detailed understanding of the invention and for an understanding of the specific manner in which the objectives of the invention may be accomplished, reference may be made to the attached drawings in which Fig. 1 is a longitudinal section through a typical internal combustion turbine driving a propeller;

Fig. 2 is a schematic diagram of one embodiment of a control system;

Figs. 3, 4, 5, 6 and 'l are schematic diagrams of alternative turbine control systems;

Fig. 8 is a schematic diagram of a temperature responsive control element;

Fig. 9 is a front elevation of an accelerometer with a cover plate removed; and

Fig. l() is a section on the line Ill-I0 of Fig. 9. Fig. l will provide general orientation on the principal components of the gas turbine and on and response elements thereof. yThe gear as shown at S2. `of torque delivered by the system is sometimes 6 axial ow turbine shown as' a non-limiting exi ample comprises a longitudinal shaft I2 carried in bearings I3, i4 and l5 forming part of the housing structure. Toward the forward end of the shaft I2, a compressor rotor i6 is secured, said rotor carrying a plurality of rows of compressor vanes I8, the rows being alternately disposed between rows of stator vanes 2Q, the stator vanes being carried by a Cowling or housing element 22 having a forward axial air entrance opening 24. Upon rotation of the shaft l2, the compressor vanes pump air into the combustion zone 26 within which combustion chambers 28 Aare disposed, the latter being fed preferably with liquid fuel through one or more pipes 3i),

the fuel iiow being regulated and controlled by a valve system 32. Fuel is supplied from appropriate tankage and pumps, not shown, through a line 34. The air for combustion of `the fuel is provided from the blower, and after .so that some air flow may pass between the engine and the cowling as through a zone d8, for

cooling the turbine, but the compressor, combustion system and turbine may be separate Afrom one another.

At the forward end of the shaft l2, a reduction gear 50 is provided, having an output shaft 52 driving a controllable pitch propeller 54. The

propeller is provided with a mechanism 56 of any 'appropriate type by which pitch angle of the 4propeller blades 53 is adjusted and by which preferably, the ptch angle of the proleller blades may be sensed or indicated. Appropriate con- -trol connections from the pitch changing sys- `tem 56 are indicated at 60.

An indication or sensing of R. P. M. of the turbine -system is necessary and this may be obtained from a gear connection to the reduction An indication or sensing necessary and this is secured by a connection '6d leading to a torque meter of conventional form embodied in the reduction gear. An indication or sensing of air mass flow may be desired in which case a unit such as 66 may be provided with connections which lead into the compressor, its outlet, or into the combustion zone or into the air intake, so that the amount and density of the air actually used by the turbine may be measured and compared with a standard datum lof density to measure air mass flow. The high pressure lead from the unit 66 would preferably have a, pressure proportional to air mass iiow, while the low pressure lead would be at an arbitrary or zero pressure. An indication of temperature of operation of the turbine may be necessary and while this temperature sensing may take various forms, a temperature measuring device 68 such as a thermo-couple is shown, r located near one of the bearing support struts in the tailpipe.

The turbine shown is merely exemplary of turbines in general and does not form the inven- 7 tion per se; The invention residesv in control systems whichk are. useable with any turbine or engine system to which such systems are applicable.

When shown in subsequent figures, elements appearing in Fig. 1y will bear the same reference characters.

Referring now'to Fig. 2., acontrol System is shown which corresponds to the fullyV comp nsated AB12 system identified inthe .introductory remarks. In this system, turbine load (propeller pitch) and fuelflow are controlled niresponse to errors betweenactual turbine speed and that set by the pilotsspeed-control lever. 'Ifhey .are also controlled simultanebuslyV byfe1,.1lsV between actual power delivered (temperature) and that set by the pilots power (temperature) control. Acceleration stabilization and compensation are applied to both turbine. load and fuel iflowi, as being typical and exemplary of derivative Sta.- oilizing control.

In this arrangement, the propeller .is shown for purposes of illustration as being hydraulically operated for blade pitchzchange. A piston- Vcylinder unit '1li is edvvith pressure iiud'through either a pipe '1,501' azpipe i8, respectively causing righ-tward or leftwardmovement of a piston .8.o whose motion is transmitted to the A.propeller through a rod 82 vand .a pin and cam-slot unit ,84. The feed ofhydraulic iiuid to the lines '15 por 1.8 is controlled byY a servo-valve 85 containing- .a valve element .88;movedbya valve control Arod 91). Fluid from a high pressure source., not shown, enters :the valve througha line S2 .and may leave the valve 86 through a line 9.4. When. the rod 9i) moves .leftwardl line- .52 is opened to line '1S causing rightward motion .of the piston 8G. Fluid is .forced from Ythe .right hand end or the piston-cylinder unit 'Eilthrough theline T8 and to vthe outlet line $14. from Vthe valve. Rightward movement of the rod y9d. will cause leftward motion of the piston Se vandits :rod 8.2 inthe same fashion. In the arrangementshown, rightward movement of the valve rod 911- will cause an increase in blade. pitch angle (beta) and viceversa. The rod 92' provides the control for propeller pitohgand isfmovedin response to.- variations in turbinespeed .and :tempera-ture, as will be described in detail hereafter.

Fuel Vowfto the'turbine is controlled byithe valve 32 fed from the. fuel source through; aline arm 95 yand-an increase in the flow of fuelto the turbine.

A Speed governor is Shown at: 163, al1-doomprises conventional iiyweights 104 swingably mounted on agear ildriven from a gear 1,0 8 which in turn is .driven at 2 Speedpronoltionel to the speedof the turbineby the turbinefbia shaft 110. A speeder spring 112 Apresses upon a .thrust bearing .114: tending .to holdl Vthe .iiy-

weights inwardly-centrifugal force resulting S from the rotation of the gear 10B will .ns the fiyweights |54 outwardly tobalarrloe Spring force. Force on the lSpeeder spring 112 is adjustable by a speed control handle |15 operating through a pinion and rack connection 118. Rightward movement of the speed control handle 116 will impose aforce upon the Speeder spring 1 12, which is unbalanced while a speed error exists, and the spring or iiyweights will -thus move a governor control rod 126 leftwardly or rightwardly respectively. When the speed setting is matched by the speed of the turbine, the force of the flyweights will balance the force of the spring 112.

The power or temperature control comprises a pilot operated handle 122 operating through a rack and pinion 124 to move a temperature control arm 125 rightw-ardly withv a call for increased temperature and leftwardly with a call V for decreased temperature. This arm 1:26 is pivcted to a cross link 128 at 1311,Y the other end of the cross link being pivoted at |32 to a rod 13.4 connected to a turbine temperature measuring device 136 which may be in the form of a servo-motor responsive in its operation to the lactual temperature of the turbine wheel or of some appropriate portion of the turbine assembly where temperature variations are proportional to those of the turbine wheel. Position of the rod 134 will be established Aby the actual temperature of the turbine. Ifo anintermediate point on the cross link 128, as at 138, a temperature or power control rod |45 is p ivoted. Axial movement of this rod will be caused by errors in temperature between the temperature measured by the device 136 and the-setting of the temperature control lever 1,22. Y

An accelerometer to measure rotational acceleration or deceleration of the turbine is shown diagrammatically at 142, this being driven'if desired through a shaft 1.43 from the gear 108. Measurements of acceleration or deceleration from the accelerometer 142 are transmitted to an Yaccelerometer servo-motor 1 44 through lines 146 and 48. A typical accelerometer arrangement for this purpose will be described-in'detail in conjunction with Figs. `9 and 10. The accelercmeter servo 1de is provided with van output rod 15D which may move-toward the left orv toward the right as shown, in response to'positive or negative accelerationof theturbine, respectively. Should derivative controls other than acceleration be used in this or another system, they would not necessarily replace the accelerometer, but would be designed into the system in an appropriate manner.

The R. P. M. control rod 29, the'temperature control rod lili?, and the accelerationrcontrol rod 15) comprise the three controlling members which move to the right or to the left, either jointly or individually, in response to errors of R. P. M. or temperature or of acceleration indications, respectively. The elements tube Vcondones, either jointly or individuai1y,'aiethe propeller pitch control rod 9i] and the fuel flow control rod Sii?. In order to connect thesefive elements together for proper interaction; the linkage in the center ofthe gureis provided. This linkage comprises a cross link 154 to the upper vend of which, as at |55, theft. P. control rod |20 is pivoted. Toward, but not at, the lower end. of the cross link 15:2, the temperature control rod iii@ is -pivoted as at 155. The cross link I54`may move leftwardly or rightwardly or may vtilt Aclockwise or eounterelockwise in .accordance ,Wthyeontrol requirements .ofthe .reds-:I 2.0 A.and 14.9, '.'loward the upper end of the cross link |54, a link |58 is pivoted as at |59, the other end of this link being pivoted as at |60 to an intermediate point on a cross link |62. The upper end of the cross link |62 is pivoted to the rod 9|) at |63 while the lower end of the cross link it? is pivoted to the acceleration control rod |59 as at |64. The lower end of the cross link ld is pivoted to a link IEE as at |161, the other end of the link |56 being pivoted as at |68 to the lower end of a cross link |10, the upper end of which is pivoted as at lli to the acceleration control rod |55. An intermediate portion of the cross link ll is pivoted as at Il?, to the fuel flow lcontrol rod |E2. By proper proportioning of the distances between the pivots of the various links androds, appropriate interaction may be secured in the system so that changes in blade angle and fuel flow will be simultaneously made in the proper amount in response to R. P. M. error, temperature error, and/ or positive or negative acceleration. The linkage dimensions indicated are the same as those appearing in the following formulae and explanation which show the interaction and stabilityl in the control system.

Qualitatively, a demand for increased R. P. M. caused by leftward movement of the rod |20 resulting from an R. P. M. error, will move the cross link |54 counter-clockwise about the point |56 as a pivot. This will move the rod 90 leftwardly calling for decreased pitch and will move the rod |62 rightwardly calling for increased fuel flow. l

A call for increased temperature due to a temperature error may be made by rightward movement of the rod |46 which will move the cross link |54 counter-clockwise about the point |55 as a pivot. This will cause rightward movement of the fuel rod |U2 effecting an increase in fuel flow and will also cause a lesser degree of rightward movement of the pivot |53 since the cross link |62 will move clockwise about the point |54 as a pivot. This will call for an increase in propeller pitch to an amount necessary to absorb the additional power occasioned by the increased fuel flow while maintaining- R. P. M. at the preset value. Simultaneous errors in either direction sensed by movements of the rods 12B and |40 will control the propeller pitch and fuel control rods S and m2 in the proper direction to compensate and overcome the sensed errors.

When R. P. M. errors exist, and when correction is initiated, accelerations will be sensed by the accelerometer |42 and will be transmitted as motion to the rod |59. This rod will vary the position of the pivots lli and |64, regulating both the pitch control and fuel control linkage inthe proper amount to exert a stabilizing and compensating influence in the regulation of R. P. M. and temperature.

In a turbine propeller control system in which R.. P. M. and temperature or their approximate manifestations are to be controlled some interaction of the controls can be experienced when the input (fuel) and output (propeller) are separately and independently controlled by tem` perature and R, P. M. error measurements. These interaction effects can be largely eliminated if, when an R. P. M. error exists or change in R. P. M. setting is made, both propeller blade angle and fuel flow are rvaried in a manner which will provide no change in turbine temperature, similarly when a temperature error exists or a change in temperature regulator setting is made both propeller blade .angle fuel flow may be varied in a manner which will produce no change in turbine R. P. M. When propeller blade angle and turbine temperature are so controlled the system may be designated as fully compensated. Under these conditions the two controls (R. P. M. and temperature) act as separate systems. Depending on the control sensitivities, the response may become oscillatory when lags are present in the system, these conditions usually being noted with the higher Icontrol sensitivities desired to obtain fast response. It is quite often desirable to use sensitivities which of themselves will produce an oscillatory condition to obtain suiciently fast respense. Since the oscillatory condition is usually undesirable it is necessary to introduce some effect (stabilizing) which will. either cause the oscillation to die out rapidly (highly damped but less than critically damped) or which will prevent the oscillatory condition 'from existing at all (over-damped or more than critically damped). A control system of the type described above having both compensation and stabilization is schematically shown by Figure 2. The control equations for this system are given below:

Referring again to Fig." 2, the coeflicients in these equations can be represented in terms of the linkage lengths as follows:

If the variation in turbine propeller parameters are expressed by the following relationships, which are linear approximations of actual conditions used to permit simplified mathematical treatment, the equations of R. P. M. response and temperature response' can be vderived. The turbine-propeller relationships are as follows:

The above equations are in a form which can be adjusted for different types of fuel systems by variation of the constants f and g. (Of particular interest are (l) fuel systems where the fuel flow is determined by the fuel -control lever position only (9:6) and (2) fuel systems in which the fuel flow is proportional to R. P. M. (one in which the fuel control lever controls the turbine driven fuel pump displacement per revolution) Eliminating vi/'f from the above equations R. P. M. and temperature equationsl are obtained as follows:

Combining these equations with the control equations the complete equations of R, P. M. and temperature become:

(sAl-sfpigrAeA-I-TBsBANG ANG and

19:37 rA==cfkgr 'sA==ak1 'u--al 56:11; lTB

Depending upon the relationship between coeiiicients in the above equations the speed and temperature response may be unstable, oscillatory, critically dampedor overdampedand in addition interaction of speed and temperature changes may be noted,

From the equation for AN it can'be seen that if a temperature regulator changelis not to introduce an R. P. M. change TA must equal TB.

Therefore,

The linkage relationship shown in Fig. `2 then becomes:

Similarly from .the equationfor ATit can be seen that if an R. P.y M. governor change is to be made without introducing afitemperature change must be zero. canlbe ldone by makingz equal tozero without interfering withotherlinkage actions.

To make uB=a the term bfle is made-equal to aor in terms of the linkages established Using the relationshipsv established, i, e. TAL-TB, 33:0 and uB=a-, the equations fortemperature and R. P. M. become:

ATR

Maintaining the relationships already. established it can be seen from theabove equations that TA can be selected to ,obtain the desired .rate of response for a temperature change. Likewise SA can be selected togive the desired rate of R. P. M. response with the value cfu. selected to maintain stable response. The relationship between uA and sA for critically damped R. P. M. response is:

or in terms of'` the linkage: shown i1LFg.'2

Other relationships between uAand SA will result in oscillatory, unstable or over damped speed changes.

Referring to Fig. 2 it is of` interest to note that for the particular example used, e becomes Zero resulting in no fuel flow change beingmade as the result of an R. P, M. error or change in governor setting. Fuel flow is changedfrom the accelerometer, however.. throughthe linkage w, U which it should also be noted isa compensating effect rather than stabilizing. With this eiect in View, the system of Figproduces thesameV result as that of Figcz.

As has been shownabove vthe use of an accelerometer or its .equivalentserves .two impor- .tantfunctions one, as part vof a 4compensating system to isolate the ktwo controls Yfrom each other and, two, as a stabilizing element to eliminate or suppress oscillatory tendencies to satisfactory levels permitting rapid response Vto changes.

Some variation'in turbine-propeller constants .can be expected with.different.light'conditions Although rnotshowninFigZ, itis entirely possible andxprobably :desirable to provide means for modifying thelinkage .(control'system constants) Las required'tomaintain .the .relationships establishedabove for different night conditions.

A complete list ofisymbols as used in the above vanalysis is as'follows,twith.theexception of s, u,

136 and a which :are non-dimensional coeiiicients and are denedby the mathematical equations given, and p whichis the ldiierential operator Aused in the analysis.

R. P. M./lb. fuel/hr.

Deg. (T)/lb. fuel/hr.

Deg. (T)/R. P. M.

Lbs. fuellhrJdeg.

Lbs. fuel/hrJR. P. M.

Seconds.

Equilibrium speed change per unit of fuel ow change with constant blade angle.

Temperature change per unit of fuel ow change at constant speed.

Temperature change per unit of speed change at constant fuel flow.

Fuel flow change per unit of fuel control lever movement at constant speed.

Fuel flow change per unit o speed change at constant lever position.

Turbine-propeller time constant (time to change 63% of total change in R. P. M. which will occur after a sudden disturbance in blade angle or fuel ow).

(In applying the above, gal; is equivalent to {l-t) CONTROL SYSTEM-GENE RAL .hand cavity 200 and ANG Change in governor speed setting R. P. M. ATP. Change in temperature regulator setting... Rankine. kv Rate of change of fuel control lever positwn per Deg. (6)/sec./deg. (T).

unit of temperature error. m Rate of change of fuel control lever position per Deg. (9)/sec./R. P. M.

, unit of speed error. la Rate of change of fuel control lever position per Dag. (0)/sec./R. P. M./see.

unit of acceleration. up Rate of change of blade angle per unit of tempera- Deg. ()/sec./deg. (T).

ure error. k Rate of change of blade angle per unit of speed Deg. (B)/sec./R. P. M.

error. Rate of change of blade angle per unit of accelera- Deg. /sec./ R. P. 1ML/sec,

ion.

CONTROL SYSTEM-LINKAGE m, q, v, 10,1, y, z Linkage lengths Inches.

Referring now to Fig. 3, a control system is shown which corresponds to a modified fully compensated AB12 system, wherein a different` type of power sensing arrangement is used responding to fuel-air ratio rather than to temperature and wherein the linkage is so arranged that acceleration stabilization and compensation are applied to both the propeller pitch control and to the fuel flow control, but wherein R. P. M. errors affect changes in propeller pitch but not in fuel flow. As in the Fig. 2 system, errors in power affect both propeller blade pitch and fuel flow.

Many of the components in this system are similar to those in the system of Fig. 2 and bear the same reference characters.

Control of power is afforded by the power lever |22 which actuates a needle Valve |80 passing through an orifice |82 fed by the pipe 30 from the fuel regulator valve 32. The downstream side of the orifice |82 connects with a fuel pipe 30a. leading to the turbine. The oriiice and the needle valve serve to set up a pressure differential. the pressure dropr being measured in a diaphragm cell 84 having a diaphragm |85. The diaphragm and cell dei-lne a left hand cavity |88 connected by a line |90 to the downstream side of the orifice |82. The cell and diaphragm define a right hand cavity |92 connected by a line |94 to the upstream side of the orice |82. The pressure drop across the orice will provide a force tending to move the diaphragm toward the left in proportion to the amount of fuel flowing through the orifice.

A second diaphragm cell |96 is provided with a diaphragm |98 dividing the cell into a vleft a right hand cavity 202. The cavity 200 is connected by aline 204,150 the sensing element |56 shown in Fig. l to provide a pressure proportional to the mass flow of air through the turbine. The cell 202 is connected to a refe-rence pressure or vacuum, also contained if desired in the unit 66 shown in Fig. 1, the connection being by means of a. pipe 206. The diaphragms of the cells |84 and |06 are connected together by a rod 208, which extends rightwardly from the cells and forms the power sensing rod I40a. having the same' general function as the power sensing rod |40 of Fig. 2. The forces produced within the cells |84 and |06 balance when fuel-air ratio equals that called for by the power lever |22 and jointly sense errors in fuelair ratio from that established by the setting of the power lever by rightward or leftward movement of the rod |4011, causing the power error responsive element to vary fuel flow and/ or propeller pitch. The above described fuel-air ratio sensing system is shown by way of example and is not intended to limit the kind of fuel-air sensing systems utilized in the invention. It provides onev of the alternate means for power sensing along with temperature sensing, torque sensing and other variables previously indicated in the introductory remarks.

As in Fig. 2, error sensing rods |20, |40a and |50 respond respectively to R. P. M. errors, power errors, or positive or negative acceleration. Likewise, elements and |02 represent respectively the control rods for propeller pitch change land fuel flow change. Thelinkage provided in Fig. 3 provides compensations which reach substantially the same end as the linkages of Fig. 2 but are arranged in different fashion. The R. P. M. sensitive control |20 is connected at 2 ||l to `a cross link 2|2 which, is pivoted at its lower end to the power control rod ||l0a as at 2M. Between the rods |20 and |40a on the cross link 2|2, a rod 2|6 is pivoted which leads to a pivot 2|8 on the lower end of a cross link 220, the upper end of said link 220 being pivoted at 222 to the accelerometer control rod |50. The propel- Y the rod S.

ler pitch control rod 9G is pivoted to the cross link 22|! between its ends. It will thus be seen that if there is no power error, an increase R. P. M. demand will rock the cross link 2|2 counterclockwise about the point 2M, moving the rod Zl leftwardly and rocking the cross link 22B clockwise about the pivot 222, thus calling for decreased beta and correspondingly greater R. P. M. Demands for control due to 'accelera tion will be imparted from the rod |56 to the rod Si) through the link 22, the latter pivoting about the pivot 2I8.

The fuel flow control rod H32 is pivoted to the lower end of a cross link 224, an intermediate portion of said link having pivotal connection with the power sensing rod Mila as at 226. The upper end of the rod 224 is pivoted at 228 to a rod `23|) extending rightwardly to a pivot 232 on an intermediate portion of a cross link 234. The lower end of the link 234 is pivoted as at 235 to a xed point while its upper end is pivoted at 236 to a rightward extension of the accelerometer control rod |56.

If there are errors in power reflected by movement of the power sensing rod Milla, the cross links 2|2 and 224 will be rotated respectively about the pivots 2|0 and 228', transmitting control motion to the beta control-rod 90 and to the fuel ow control rod |02. Acceleration of the turbine in either direction moves the acceleration rod |50 and will not only cause change in blade angle as previously described but will also effect changes in fuel flow through the cross link `234, the rod 238 and the cross link 22d.

Referring now to Fig. 4, a control system is shown which corresponds to the`B12 system previously mentioned in the introductory remarks. In this system, the speed control 'and governor act upon the fuel regulator,'and the pilots power control affects both propeller pitch and fuel iiow. Regulator interlinkage is provided so that errorsin power initiate corrections in both blade angle and fuel ow in the proper proportions while errors in R. P. M. initiate correction of fuel iiow. Many of the elements shown in Fig. 4 are common to those shown in Figs. 2 and 3 and the same reference characters are applied. The interlinkage, however, is'somewhat diiierent as will now be noted. The cells 84 vand |95 which, as shown, provide the means for detecting errors in fuel-air ratio or power, are connected by a rod Ilia directly to the control rod 9o for propeller pitch control and are connected through links 240, 24| and 242 to the fuel valve rod M22. Thus purposeful changes Vor externally imposed variations in power will be applied directly to change pitch of the propeller, and through the linkage, to change fuel flow. .As hereinbefore noted, the fuel-air ratio measurement is only one of several manifestations Yof power which can be used for sensing. The speed governor 93 is provided with the rod |212 which is movable axially in response to errors in turbine speed from the desired speed set by the sneed lever H5. this rod |20 being connected at 243 to the upper end of the cross link 242. The lower portion of the link 242 as described is connected to the valve rod |il2 of the fuel control regulating valve |20 which causes changes in fuel flow to correct R. P. M. errors. portion of the cross link 242 is connected as at 24F, through the link 24|, to the cross link 2Go as at 225. This cross link at a point intermediate its ends is connected at 246to a continuation of The servomotor HM `of the accel- Another e 16 erometer iS Connected through a rod |50 to the upper end of .thelink 240.

Deviations in R. P. M. sensed by the governor, either due to purposeful .changes of the speed control H5 or to externally imposed variations, will act to alter the fuel flow. .Any acceleration or deceleration in speed will be sensed by the accelerometerand Will apply corrections'in the appropriate direction to the fuel ow mechanism. This system differs from the AB12 system previously described bythe fact that errors in R. P. M. cause changes in fuel iiowY without concurrent changes in propeller pitch. Power errors demand changes in both fuel iiow and blade pitch through the action of the rods |49@ and on the pitch and fuel flow systems. There is sufiicient crosslinkage in the system so that satisfactory operation may be expected.

Referring now to Fig. 5, a control system is shown which corresponds to the A12 system previously mentioned in the introductory remarks. Interlinkage is provided so that errors in power initiatecorrectionsin both blade angle and fuel flow in the proper proportions while errors in R. P. M. initiate correction of propeller pitch. Some of the elements of Fig. 5 are common to those shown in prior gures and'where appropiae, the same reference characters are app 1e In Fig. 5, an electrically controlled controllable pitch propeller is shown in lieu of the hydraulic type of the other iigures. The particular type of propeller is immaterial to the control system functioningeither mechanical or-electrical or hydraulic propellers may be used in any one of the embodiments of the invention. The propeller blades 53. are changed in pitch by an electric motor 523 operating on the blad@ gears thrcugha speed .reducer 5m. Electrical oonductors 5|2, 5M and 5|5, passing through a slip ring assembly 5|8, respectively provide decrease pitch current, increase pitch current and a coinmon return. The return wire 5| connects with a power sour-ce 520 and thence to ground and to the terminal of a switch arm 522 operated by the arm v9E connected to the control system. The switch. arm may lcontact either an increase pitch switch point 525 or a decreaseY pitch switch point 528 respectively connected to the wires 5M, and SI2. Closure of the switch arm 522 with one or the other of the switch points energizes the motor 528 to produce pitch increase or pitch decrease of the propeller. A rate of pitch change proportional to the off-speed error may be secured by means known in the propellergoverning art.

The speed governor |23Y as previously described,

.may be adjusted for a desired speed by the speed control lever H5. Errors in speed from the preset value result inaxial movement of the governor rod |2| linked to a cross arm M8 which is in turn linked to the accelerorneter servo-motor rod ISB and to a rod 255i connected to the switch operating rod 9S through a cross link 25|. Thus speed errors and acceleration signals are transmitted to the propeller pitch chf/uitging.mechanismv to initiate pitch corrections.

Leading from the valve cylinder |99 is the fuel control rod |62 which is directly connected to the rod Mila leading to the fuel-air ratio sensing device or equivalent power sensing means, as represented by the diaphragm cells les |95. Errors in power sensed by the elements |84 and |96 cause direct operation of the valve |00 with consequent operation of the fuel servomotor 98 and change in the rate of fuel flow through the fuel valve 32. Concurrently, the powersensing system initiates blade pitch corrections through the cross link 25| which is pivoted to the power sensing rod |40a at 252.

This system differs from the AB12 system Dreviously described by the fact that errors in R. P. M. cause changes in blade angle without concurrent changes in fuel fiow unless power changes demand the changes in fuel flow. Errors in power cause concurrent changes in fuel flow and propeller pitch. There is suiicient cross linkage in the system so that satisfactory operation may be expected.

Referring now to Fig. 6, a control system is shown which corresponds to the A1 system previously mentioned in the introductory remarks. In this system, a speed control and governor, and an accelerometer act upon propeller pitch and the power control and sensing device act upon fuel now with no control system cross linkage as in other embodiments. This system is simil-ar to the conventional engine power plant system except for accelerometer stabilization and operates satisfactorily in such systems due to the decreased importance generally attached to 'the inter-independence of the power and R. P. M. responses. In a turbine system an arrangement rsuch as that in Fig. 6 may be satisfactory when acceleration stabilization is applied to the governor as shown. Propeller pitch vis adjusted by the servo-motor 14 which is operated by a valve unit 86 whose rod 90 is connected to a cross link 259 connected to the accelerometer rod |50 and the governor rod |29, the governor |03 being driven in any appro- `private manner as by the gear |03 and a shaft driven by the power plant. Fluid for operating the servo-motor 14 is supplied and scaVenged, by a pressure line 92 and a scavenge line 94, connected to the valve 85 as shown.

The diaphragm units |84 and |96 previously described as providing a means for sensing power, sense fuel-air ratio and the power lever |22 operates to create a demand for increased or decreased power as previously described. A rod |40a from the fuel-air ratio sensing device is directly connected to the movable valve rod |02 for operating the valve |00, the latter` being -connected as shown to the servo-motor 98 whose output rod 91 is connected to the arm 96 of the fuel valve 32 which controls the flow of :fuel-.from the supply to the turbine. Accelera- -tion stabilization is imposed on the speed con- -trol as previously described. With acceleration vstabilization or equivalent, this system operates satisfactorily as to stability and fast response. However, to prevent severe overspeeding, sud- 4denchanges in power demand should be avoided. Also, to minimize harmful temperature rises, demands for sudden R. .P. M. change should be iavoided.

Referring now to Fig. 7, the control system -shown corresponds to the Bd2q system previously mentioned in the introductory remarks. As -there noted, this system is a modification of a .B2 system to attain superior response speed, and fstability.l In this system, the' speed control and governor actupon the fuel regulating valve, and

. the power control and torque sensing device act upon propeller pitch. There is no direct interlconnection `betweenthe power control element and the speed control elements. The upper porftion of Fig. '1 includes an R. P. M. control lever |15 variable to adjust the force imposed on the ilyweight unit |04 by the speeder spring ||2. The speed errors sensed by the governor are transmitted by the rod |20 directly to the lever 96 olf the fuel valve 32 which regulates the fuel flow from the fuel line 34, from the fuel supply, to the fuel line 30 leading to the turbine power plant. The schematic representation of Fig. '1 provides a simplified direct acting droop governor-in practice a servo-system would be incorporated, retaining the droop characteristics. In this arrangement there will be a direct proportional relationship between the amount of fuel feed to the turbine and the difference between the actual R. P. M. and the preset R. P. M. The arrangement is such that excessive turbine speeds will cut down the flow of fuel. This type of governing is described as a droop type vbecause a curve of turbine R. P. M. versus power for a fixed governor setting Iwill show a falling off or droop of the R. P. M. curve as the fuel requirements are increased. This droop effect may be made only temporary by the addition of slow acting resetting devices for the governor, not shown.

In the lower part of Fig. '1, the -power -or torque lever |22, controllable Iby the pilot, moves a rack 212 to adjust the force of a spring 214 acting through a rod 210 on a diaphragm 218 contained within the housing 280. The left side of the housing is provided with a line 282 extending to a turbine torque meter 64 such as is indicated in Fig. 1. Torque meter fluid pressure entering the line 282 acts upon the left side of the diaphragni 218, opposing the compressive force imposed by the spring 214. The diaphragm 218 is connected by the power sensing rod |40b to the valve rod controlling propeller pitch. When torque meter pressure and spring pressure balance, the valve 8B will be closed and the propeller pitch will not change. Unbalance between torque meter and spring pressure due to torque errors will cause lblade pitch change, in a direction to correct the error. A greater torque output from the turbine than that called for -by the setting of the control |22 will move the valve rod 90 to the right, to cause a decrease in pitch relieving the torque load on the turbine and restoring it to the preset value.

The inherent stability of the type of system shown in Fig. '7 is excellent and while the R. P. M. and torque controls are not directly interconnected, the responses of the control system to errors in R. P. M. or power will' 4be fast, and

variation of one factor will not induce oscillatory response in the combined controls, avoiding any great need for accelerometer stabilization.

All the systems described in the several figures are susceptible to considerable modification. Such modications may include, where not already shown, a power sensing system responsive to errors in torque output of the turbine and ,the governor may be modified to the droop type wherein changes in fuel quantity are `affected rather than changes in fuel rate, in response to R. P. M. errors. Such modifications are particularly appropriate in the B2 system, identifying it, then, as a Bd2q system just described.

AThe torque, temperature or fuel-air ratio power control may be used in any of the systems, and

the electric or hydraulic or any other propeller type may also be used in any of the systems.

In any of the systems previously described, provision has been made for control in the normal power range between minimtun and maximum power. In actual installations of turbinepropeller units in aircraft, provisions should be made for zero power lever position along with regulation oit-power to zero or very `low minimum value. Provision also shouldv be made, in the case of reversible pitch propellers, for changing themode of power control so that power will be limited -by anticipated propeller stresses due to reverse thrust in addition to limitations imposed lby turbine wheel temperature. Further power limitations may be required according to the structural ability of other turbine parts such as reduction gears to sustainY high torque. Decrements in permissible power may be necessitated by long usage f the turbine, with consequent inability to sustain the high -power level of which kit Iwas Ycapable when new. In some installations, a tail-cone may be provided to adjust-the division offpower between that delivered-to the propeller and that delivered as pure Vjet. Control modifications will be desirable in such arrangements Lto compensate for the effects of the `tail cone positionor turbine temperature and R.` P. M.

'8 illustrates an arrangement for sensing turbine temperature and for providing a -control for lthe pres-etting of desired turbine' temperature. Such a control arrangement comprises a power control as incorporated in an A312 system such `as shown in Fig. 2, or in other systems, in lieu of other sorts of power sensing and control devices. For instance, the system of Fig. 8 could bhefsubstituted Lfor the fuel-air measuring cells |84-and |06 and the elements |24, |26 and |28 in 3l and Yassociated elements of that system.

In Fig. '8, a thermo-couple or equivalent 68 (shown in Fig. 1) is operatively connected to a Vtemperature indicator 300, the indicating arm 302 o f `which is linked to the arm |34-pivotally connected to thev cross l-ink- |28 at one end thereof asat |32." The other end of -the link |20 is pivot- `ally connected to the link |26 at |39, connected in turn to the control lever |22. An intermediate portion of the Vcross link |28 is connected to lthe power control such as the rod |40 as at i 38. The rod |40 affects either or both, the fuel control 4and the turbine load control system to secure interrelated action between the fuel flow control land load or -blade pitch control.V The operating handle |22 may be moved to any desired power `setting which corresponds to a turbine temperature appropriate for such a setting. The link |28 is swung about the pivot |32 4between the rod |34 `andflthe 'link |28, altering the fuel flow and/or turbine load to cause its adjustment for anew turbine tempera-ture setting.` As the new turbine temperature setting is approached, turbine teinperature will reflect in the thermo-couple 68 Vor its vequivalent and'thence into movement of the arm 302, shifting the pivot |32 until fuel ow and/or turbine load is stabilized at the new turbine temperature setting. Thereupon, no further adjustment in fuel flow and/or turbine load will occur until further changes in conditions are enforced or occur due to external influences. s

' In the present state of the art, thermo-couples and temperature sensing devices have considerable-lag and do not produce suiciently fast'and precise indications of temperature to prevent turbine temperature overshoots, unless compensations are incorporated in the system forthe delayed action. Such compensation can be incorporated. Assuming that fast responding temperature sensing devices are available, the system shown in Fig.. .8. can be used in anyone of the control .systems herein described.

vAn example Aof 4an accelerome'ter to sense rotav2() tional accelerationv and deceleration `ofthe tuxfbine'is shown in` Figs. 9 and 1'0. This unit, while suitable lin the `environment of a turbine `control system, has general` application in any mechanism where such an` accelerometer is needed; The unit comprisesa housing rllllhaving afbell 402 and a cover 404 kat one end, `thebell containing a plate 406 secured Ona-shaft ilidriven bysa. turbine or other rotating partwhoseiaccelerations anddecelerations are to be-sensed. On Ya,..stu'b shaft409 on the plate 406, amassive disc '4.||Jis mounted for.. free oscillation. Said disc-carries a projection 4|2 near itsperiphery, which .may move between stopposts M4I and 4116. mounted onthe plate 406. Said posts respectively-have ports facing the projection 4|2, whichconnect with and form part. of passagesdlvand 420..lead, ing rthrough the plate 406 and the shaft. 40.8 to ports in the shaftregisteringwith annulargrooves in the housing, said grooves respectivelyhaving connections 422. and424.

The housing 400v contains a pairofsimilar pumps 426-and 428. whose output ldependsnpon R. P. M. and not on back pressure,` having a com- .mon suction line430. leading toa fluid ,supply .432',

and having separate4 deliverylines. 434.and435 respectively connected to` the connections 422 and 424.. The `latter also connect respecti-velyto closedcells 43B and 44.0 withintheaccelerometer motor |44 (referred .,toinpreviouslsystem drawings). The cells I3-Band A40-are separated-by a piston or diaphragm 444, provided with centering and calibrating springs ifdesired. The piston -is movable in response to pressure .differences between the cells, thepiston thus being `ablewtu move the piston rod |51!) which transmits ,acceleration responses to any appropriate mechanism.

When the plate i406 rotates atsteadyv speed, .the disc 410 will rotate therewith and the projection 4|2 will center between the posts 414 and All-6, providing equal bleed of fluidfrom the posts. Upon rotational acceleration or deceleration of the plate 406, the disc will lag orlead plate rotation, closing off one of the post portsand opening the other an amount depending on the-magnitude of acceleration or deceleration, thus causing. 'a proportional pressure difference inthe vlines fr422 and 424, and in the cells ,438, and 4,40.

Bleed from theports4|4 and 4 I0 passes into. the bell 402, whence it is scavenged tothe. Apump intakes by a connection 446from .the bell tov theline 430.

Though several modifications of thein-vention are shown, itis to be understood :that the. invention may be applied in various forms and in various environments.` Changes may bemadein the arrangements shown without departing, from .the spirit-of the invention. Reference should be had to the appended claims for definitions of the limits of the invention.

What is claimed is:

l. An internal combustion turbine, avariable load driven there-by, variable means to vfeed fuel thereto, control means to preset a 'certa-in operating speed and to preset a certain manifestation of turbine tempera-ture, means responsive respec- V tively to Adeviations in turbine speed Vand turbine sive transient speeds and vtemperature with sub- 'means stantially'instantaneous response in said responsive means.-

2. An internal combustion turbine, a variable load driven thereby, a variable fuel feed thereto, a sensing device for turbine speed, a sensing device for the fuel-air ratio delivered to said turbine, means to preset a desired turbine R. P. M., means to preset a desired proportion of full turbine power at the preset R. P. M., and means operable to adjust said load responsive to deviations in speed from the preset R. P. M. as noted by said speed sensing device, and also operable to adjust both said load and fuel feed responsive to deviations in fuel-air ratio as noted by said fuel-air ratio sensing device, to restore the preset power and speed.

3. An internal combustion turbine, a variable load driven thereby, a variable fuel feed thereto, a sensing device for turbine speed, a sensing device for the temperature of the turbine, means to preset va desired turbine R. P. M., means to preset a desired proportion of full turbine power at the preset R. P. M., and interacting means operable to adjust both said load and fuel feed responsive to deviations in speed from the preset R. P. M. as noted by said speed sensing device, and responsive to deviations in temperature of the turbine wheel as noted by said temperature sensing device to restore the preset power and speed.

4. In an internal combustion turbine having a variable load and a variable fuel flow, a sensing device for turbine speed, a sensing device for the temperature of the turbine combustion system, means to preset a desired turbine R. P. M., means to preset a desired pro-portion of full turbine'. power at the preset R. P. M., interacting means operable simultaneously to adjust both said load and iiow, said interacting means being responsive -to deviations in speed from the preset R. P. M. as noted by said speed sensing device and also responsive to deviations in temperature of the tur-` bine combustion system as noted by said temperature sensing device to restore the preset power and speed, and means responsive to acceleration and deceleration of the turbine arranged to modify the operation of said interacting means.

5. In an interna1 combustion turbine having a variable load and a variable fuel flow and including respectively load and flow adjusters, a sensing device for turbine speed, a sensing device for a manifestation of turbine power output, manual means to preset a desired R. P. M., separate man- .ual means to preset a desired proportion offull turbine power at the preset R. P. M., and interacting means connected to said sensing devices operable to adjust both said load and flow adjusters jointly responsive to deviations in speed from the preset R. P. M. as noted by said speed sensing device, and responsive to deviations in power output as noted by said power sensing device to restore the preset power and speed.

6. An internal combustion turbine, a variable pitch propeller driven thereby, a variable fuel feed thereto including respectively propeller pitch and fuel feed adjusters, a sensing device for turbine speed, a sensing device for a factor of the power absorbed by said propeller, manual means to preset a desired turbine R. P. M., separate manual to preset a desired proportion of the factor of full turbine power at the preset R. P. M., interconnections between said propellerfpitoh and fuel adjusters, and means connected to said sensing devices Voperable to adjust said propeller vand.

feed jointly responsive to deviations in speed from:

bine having a compressor for ambient air, combustion chambers to which said fuel and a portion of the compressed air is delivered for burning, a turbine driven by combustion gases and substantially the balance of the compressed air, means to drive said compressor and the said variable load fromthe said turbine, means to preset a certain operating speed, means to preset a certain proportion of maximum power available under any operating condition of ambient'.

air speed, density and temperature, a power sensing means, and a speed sensing means, said sensing means being interconnected and comprising mechanism to alter said load and fuel flow in response to variations in turbine speed and `power from said preset values, to `bring said speed and power to said preset values.

8. A turbine according to claim 7 wherein at least one of said sensing means is biased by means responsive to acceleration and deceleration of the turbine. *A

9. A turbine according to claim 7 including an accelerometer sensitive to turbine acceleration and deceleration, and a servo-motor actuated by said accelerometer and connected to the interconnected sensing means to impose variations in said turbine load.

10. An internal combustion turbine, a variable load driven thereby, a variable fuel feed thereto, means to preset a desired value of turbine speed, means to preset a desired level of turbine power, means to sense deviations in power from the preset level and connected to the variable lo-ad to alter turbine load to restore power to the preset level, means to sense deviations in R. P. M. from the preset level and connected to the variable fuel feed to alter fuel feed to restore R. P. M. to its preset value, means connected to the turbine to sense positive and negative turbine acceleration'upon speed uctuations thereof, and means connecting said fuel feed and said acceleration sensing means further to alter the fuel feed toward restoration of speed to the preset value.

l1. Aninternal combustion turbine, a variable load driven thereby, a variable fuel feed thereto, means to preset a desired value of turbine speed, means to preset a desired level of turbine power, means to sense deviations in power from the preset level and connected to the variable fuel feed to alter fuel feed to restore the power to the preset level, means to sense deviations in R. P. M. from the preset level and connected to the variable load to alter turbine load to restore R. P. M to its preset value, means connected to the turbine to sense positive and negative acceleration upon speed fluctuations of the turbine, and means connecting said acceleration sensing means further to alter the variable loadtoward restoration of R. P. M. to its preset value.

12. An internal combustion turbine, a variable load driven thereby, a variable fuel feed thereto, means to preset a desired value of turbine speed, separate independent means to preset a desired level of turbine power, means interconnecting said variable load and variable fuel feed, means to sense deviations in speed from said preset value and jointly to alter turbine load and fuel feed through said interconnection to aman-.afm

resterai-.he speedto; the preset value, and means to.,-.se.nse, deviationsl inA power from saidrpreset level connected to alter fuelfeedto restore the nowentogits preset value.

13. An internal combustionY turbine, a variable load; driven thereby, al variable fuel feed thereto, means `to preset la desired-value of `turbine speed, separate independent means to preset a desired level of turbine power, means to sense deviationsinspeedffrom said preset value and to alter turbineload vand fuel feed to restore the speed t;the,preset,va1ue, means to sense deviations in power from said; preset level and to alter fuel feed 'to` restore the power to its preset value, and-means responsive to turbine acceleration to assistv in restoringy speed, and fpower to their preset. values.

lfi.v An internal'combustion turbine, a variable loadgdriven thereby, a variablefuel feed there;- to, `means topreset a desired value of turbine speed, means to preset a desired level of turbine power, means to sense deviationsY inxspeed from Said preset value` and to alter-turbine load and fuel feed to restore the speed to the preset value, meansto sense deviations in power from said preset; leveland-toi alter turbine load to restore the power to itspreset level, and'means responsive to turbine accceleration to assist in restoring speed and )power to their preset. values.

15.. vAn'internal combustion turbine, a variable loaddriventhereby, avariable fuel feed thereto, means to preset 'a-'desired value of turbine speed, means -to preset a desired level of turbine power, means to sense deviations in speed from said .preset value, a connection lbetween said speed sensing-means and said variable fuel feed to-.alter fuel feed .t0 restore `the speed to its presetivalue, means 4to sensezdeviations in power from saidpreset level, -a connection from said powersensing means "to both said variable load and said variable fuel feed to alter turbine load and fuelfeed to `restore the power to its preset level, and means responsiveto turbine acceleration-connected to one of said sensing means to assist-'in restoring speed and power to: their preset values.

16; An internal combustion turbine, a variable load1d-riven thereby, a'variable fuel feed thereto, separate independent controlmeans to select a certain operating speed and-tov select a certain manifestation v of.- turbine temperature, means to .sense vactual :speed and to. sense. actual manifestations* of" turbine: temperature, means responsive to differences- :b'etween'tlie `preselected andactual j speed to :alter fuel feed and turbine load-iin'such proportions asto restore. the speed to .theselected 'value without alteraticnof the temperature manifestation, and means responsive to differences between preselected and actual temperature manifestations to .alter fuelifeed and turbine. load in such proportionsras to restore the temperature. mainfestation Vto. the selectedvadue without alteration of the speed.

Vl'?. An internal combustionturbine, afvariabl'e load driven thereby, a variable fuel ffeed thereto, a controller to seta desired speed of turbine operation, av controller to set `a desired power levelatwhi'ch the turbine is to `operate while operating at'th'e desired speed, `means connected to said fuel feed to adjust vsaid fuel feedY in response to deviations in turbine, speed from the value established by saidl controller, acceleration responsive means to produce a stabilizing4 control quantity derived fromA speed deviations,- means connecting said acceleration responsive means; with .saidzfuel;` feed to. enable.I said controlv quantity to effect further variations inzfuelfeed, and-means connectedto adjust said load in response to deviations vin power from the value established Yby, said controller.

13. An 'internal combustion turbine, avariable load driven-thereby, a variable fuel-feed thereto, control-means tofset a desired level of turbine speed, controlmeans, operable independently-of the speed ycontrol means, to set any one of a plurality of desi-redlevels 'of turbine tempera'- ture,vineans vto-sense actual turbine speed, means tosense actual Vturbine temperature; and means actuated by difference between set speed and actual speed, and between set temperature-and actual temperature, to adjust said variable load and variable fuel `feedconcurrently and in proper proportion torbring vthe set and actual speeds into vcoincidence and to` bring the-set vandjactual temperatures into coincidence.

19.r Anfinternal combustion turbine, a variable load driventhereby, a variablefuel feed thereto, control meansto seta-desired level of turbine speed,` :control means operable independently of the speed: control means vto set any one of `a plurality of desired 'levels of `'turbine temperature,` theffpower. output of said `turbine being variable dueto Vdierencesin operating conditions even whenoper-ating at t'heset levels of speed vand temperature, an actual speed sensing device, a sensing device to sense :a manifestation-of actual turbine temperature, and means controlled' by saide'sensingdevices toy adjust said variable load and-variable--fuel feed-to .produce turbine operation at Y thecset ,levels zof turbine; speed and temperature.

v20. Aninternalcombustion turbine, avariable load driventhereby; a variable fuelY feed thereto, mean-'to senseeth'exactual turbine speed, `means to sense a, manifestationof actual turbinetemperaturej control means to preset any one of several different desired speedV levels, separate independently operable control means to preset any oney of several different desired operating temperature levels, and'means controlled byiboth saidf sensing: means; responsive to deviations thereof i from*v respective' speedY and.` temperature control means settings, to Vary said' load and-to vary'saidfuel flowz'in-amount vtoV cause turbine speed: andA temperature-:to:,reach thelevels preset by respectiveA speed'. and temperature control mea-ns;

2l.: ,An internal combustion turbine, a' variable loadfdriven thereby, ,a variable,V fuel feed there; to, means to Vsense actual-turbine speed; `means to" sense a.function of actual turbine power at af presetspeed;- control means to preset any 'one of several 'different' desiredispeed levels in vthe normal range, separate independently operable control means to preset any one of f several different desired normal operatinglevels. of a function-of turbine-power, con-nections vbetween said speed sensing ,means .and .said variable .load .and said variablefuel feed, and connections between said powersensine means andsaid variable load and said variable fuel feed, to vary said loadand to vary said `fuel now in. amount to Vcause turbine speed and turbinepowerfunction toreachrthe levels presetby-respective'speed and power function control means.VV

22; An'internal combustion turbine having in combination agvariable .load driven thereby, a variable fuel feed for theturbine, an adjustable speedcontroll'er to selectva `desired oper-ating speed,4 'a--separate adjustable power. controller.; to 

